STUDIES ON INDIAN-OCEAN MANGANESE NODULES - 11 - PHYSIOCHEMICAL CHARACTERIZATION AND CATALYTIC ACTIVITY OF SILVER-OXIDE MIXED MANGANESE NODULES

The promoting effect of Ag2O on the physicochemical properties and cat alytic activity of manganese nodules has been investigated. The surfac e area and surface oxygen increased with addition of Ag2O, reaching a maximum at 1 mol% of Ag, and then decreased with further addition of A g2O. The catalytic activity of manganese nodules substantially increas ed with addition of Ag2O over a wide range (0.25-25 mol% Ag). Addition of only 0.25 mol% of Ag to the nodule decreased the temperature of co mplete CO oxidation from 350 degrees C to as low as 100 degrees C. Thi s enhanced activity was explained by the concerted action of Ag and Mn , where CO was preferentially adsorbed on Ag2O and oxidized. The reduc ed Ag was then reoxidized rapidly by oxygen transferred from Mn. The p romoting effect of Ag2O on H2O2 decomposition and ketonization of acet ic acid, however, was less pronounced, (C) 1998 Academic Press.